1. Field of the Invention
The present invention relates in general to an apparatus which spaces, locates and aligns one or more magnet coils concentrically within the bore of a main magnet coil of an MRI machine. The invention more particularly relates to such an apparatus which further concentrically positions a specimen tube accurately within the MRI bore along predetermined axial and radial planes for optimum imaging of the specimen.
2. Description of Prior Developments
In some magnetic resonance imaging (MRI) machines, a removable gradient coil is axially movably mounted with the bore of the main magnet coil with a simple sliding friction fit. This adjustable and removable fit allows an operator to selectively replace or interchange various gradient coils within the bore of the main coil to optimize the MRI machine for selected imaging applications.
While this feature has proved useful, it requires considerable time, effort and expertise to accurately reposition and install one replacement gradient coil in place of another. Prior replaceable gradient coils required trial and error adjustment of the axial position of the gradient coil within the main magnet coil bore, making repeatable imaging results difficult to achieve.
Even further adjustment of prior MRI machines was needed to accurately axially and cumferentially position and hold a specimen within the main magnet coil bore to achieve optimum imaging of the specimen. This problem is particularly, difficult in the case of laboratory animal specimens being imaged in the MRI machine, as the area being imaged is quite small. For example, the area imaged to cover a rodent brain is quite small and requires accurate adjustment and positioning within the MRI fields.
In order to further shape, condition and focus the magnetic field within the main coil bore, an additional coil, referred to as a probe coil, surface coil or radio frequency coil can be provided within the main coil bore. This coil must be carefully aligned axially, radially and circumferentially (clockwise) within the main coil bore and further carefully positioned with respect to the gradient coil and with respect to the specimen being imaged. Alignment of this probe coil has required considerable time, effort and expertise.
In some cases, it is desirable to interchange various probe coils to adapt the MRI machine for specific applications. It can be appreciated that such replacement can involve considerable time, effort and expertise in order to achieve optimum alignment with the other magnet coils and with the imaging area of the specimen.
In each of the cases noted above, the respective coil and specimen positioning and locating procedures must not only be accurate, but also highly repeatable so that results may be accurately duplicated for verification, sampling and proofs. Because of the trial and error positioning of magnets and specimens associated with prior procedures, accurate repeatable imaging results have been difficult to achieve.